The topic of safety is becoming increasingly important in machine and installation construction. Accordingly, the demands imposed on safety standards which need to be complied with and are used for personal protection but increasingly also to protect material assets and the environment are also increasing.
The aim of functional safety is to minimize or eliminate risks which can arise both during undisturbed and during disturbed operation of machines or installations. Some previously known techniques primarily achieve this by means of redundant systems. Moving axes in safety-oriented applications therefore require redundant position information in order to be able to perform corresponding safety functions. Different system configurations can be implemented in order to obtain independent position values. One possibility is to use two measuring devices per axis. However, a solution with only one position measuring device is strived for in many cases for reasons of cost. Such position measuring devices can produce so-called sine/cosine signals by scanning a material measure having markings arranged periodically in the measuring direction using sensors which are spaced apart.
U.S. Pat. No. 6,295,992 B1 discloses a position measuring system in which sine and cosine signals are produced and evaluated by scanning a material measure. The sine and cosine signals may be preprocessed in order to improve the measurement result.
It is desirable to specify a measuring apparatus for positions and/or speeds which is functionally safe and nevertheless provides measured values which are as accurate as possible.